Recently, endoscope apparatus have been widely spread for performing observation and processing on an observed part by inserting an inserting portion to the observing part within a body cavity, for example, and by transmitting illumination light from an illumination light transmitting unit, such as a light guide fiber flux and irradiating it to the observing part from the distal end of the inserting portion so as to obtain an image of the observed part.
One of the endoscope apparatus is an electronic endoscope apparatus, which is provided with a solid image pickup element at the distal end of the inserting portion such as a CCD, forms an image of an observed part on an image pickup surface by using an objective optical system and converts it to electric signals. By performing signal processing on the electric signals, the image of the observed part can be displayed on a monitor, for example, and/or can be stored in an information recording device or the like as image data.
For example, in the field of surgery, there is provided a surgical rigid endoscope apparatus for displaying an image of an observed part on a monitor, for example, by inserting a rigid inserting portion of a rigid endoscope to the observed part within a body cavity or the like, transmitting illumination right by an illuminating light transmitting unit and irradiating it to the observing part from the distal end of the inserting portion, transmitting an image of the observed part to an ocular portion by using an image transmitting unit, such as a relay lens, from the distal end of the inserting portion and capturing the image of the observed part by using a CCD of an external TV camera, which is attached to the ocular portion removably.
For example, in Japanese Patent Application No. 11-182333, which was filed by the present applicant before, an image processing apparatus was disclosed for performing signal processing on an image signal by driving multiple kinds of CCD of the electronic endoscope apparatus or the surgical rigid endoscope apparatus.
In Japanese Unexamined Patent Application Publication No. 10-118032, a medical image display apparatus was disclosed for displaying on a monitor a main image and a sub-image in Picture-in-Picture.
However, in Japanese Patent Application No. 11-182333, processing is performed by synchronizing and driving drive clocks in all of the CCD's and by synchronizing signal processing clocks of a signal processing circuit. Yet, some CCD's can be driven only by a predetermined frequency. Thus, there is a problem that such a CCD cannot be used in some cases.
In Japanese Unexamined Patent Application Publication No. 10-118032, it is assumed that both main image and sub-image in Picture-in-Picture are images to be displayed on an entire area of a monitor as video images. In this case, a part of the image area of the main image cannot be viewed because of the sub-image. However, in an endoscope, a CCD is used in which an image is not displayed on an entire area of the monitor. A method has not been disclosed for using the area on the monitor effectively in that case.
The present invention is made in view of the above-described matters. It is an object of the present invention to provide an image pickup system, which can drive CCD's by using a predetermined frequency even when a camera head (or an electronic endoscope) using multiple kinds of CCD are used and which can perform a signal processing clock of a signal processing circuit by using one kind of clock.
It is another object of the present invention to provide an image pickup system, which can construct an image in Picture-in-Picture effectively in an endoscope for which an image is not displayed on an entire area of a monitor.